Shuttle device



United States Patent SHUTTLE DEVICE Knut Henrichsen, Los Angeles,Calif., assignor to North American Aviation, Inc.

Application September 14, 1953, Serial No. 379,964

13 Claims. (121-157) This invention pertains to a shuttle device andmore T particularly to a hydraulically actuated shuttle device havingrapid action.

This invention is intended for use where a particularly fast actingshuttle device is required. For example, there may be a reciprocalhydraulic motor which requires a fast valve action so that there will beno appreciable time taken up in supplying the actuating impulse to themotor at either end of its stroke. The shuttle device of this inventionis adapted to operate such a valve and is further adapted to operatevarious mechanical devices. This shuttle is designed to operate when areciprocal member reaches the end of its stroke in either direction.This reciprocal member may travel through a relatively long and slowstroke, but when the operation of the shuttle takes place the latterwill pass through a relatively short stroke with great speed. Thisshuttle is adapted for operation by fluid pressure, preferably hydraulicfluid, and is subjected to full pressure from the fluid throughout itsstroke in either direction.

Accordingly it is an object of this invention to provide a fast-actingreciprocal shuttle devices Another object of this invention is toprovide a shuttle device which moves rapidly through a short stroke whena trigger member is moved more slowly through a long stroke.

A further object of this invention is to provide a hydraulicallyoperated shuttle adapted for operating a valve or other mechanicaldevice.

Still another object of this invention is to provide a shuttle devicewhich is subjected to operating forces throughout and at the terminationof its stroke.

These and other objects will become apparent from the following detaileddescription taken in connection with the accompanying drawing in whichFig. 1 is a sectional view of a pump and motor combination utilizing theshuttle of this invention,

Fig. 2 is a sectional view taken along line 22 of Fig. 1,

Fig. 3 is a sectional view taken along line 3-3 of Fig. 1, illustratingthe shuttle device,

Fig. 4 is a fragmentary sectional view showing the shuttle in anintermediate position of its stroke,

Fig. 5 is a fragmentary sectional view showing the shuttle at one end ofits stroke and the trigger member at the opposite end of its stroke,

Fig. 6 is a sectional view illustrating the porting action effected bythe shuttle member at one end of its stroke, and

Fig. 7 is a fragmentary sectional view illustrating the porting actionof the shuttle member at the opposite end of its stroke.

Referring to the drawing, the shuttle of this invention is illustratedas used with a hydraulic motor and coupled free piston pump. The actionof the shuttle of this invention can best be understood by firstobserving the operation of the motor-pump assembly. This latter unit, asshown in Figs. 1 and 2, includes a housing 1 which is "ice provided withtwo inlet ports 2 and 3 and two outlet ports 4 and 5 adapted forconnection with suitable fluid lines. Reciprocal within housing 1 is afree piston 6 which serves to pump the fluid from the inlet ports to theoutlet ports. The inlet ports and the outlet ports all are provided withsuitable spring-loaded valves 7, 8, 9 and 10 which will permit fluidflow in one direction only. Thus it is obvious that when the piston 6 istraveling to the left from the positionillustrated in Fig. 1, the fluidon the left side of the piston will be forced outwardly through the port4 and will be drawn'inwardly to the right hand side of the pistonthrough inlet port 3. At the same time valves 8 and 10 prevent fluidflow in the reverse direction through ports 2 and 5. If the piston ismoved to the right fluid will be forced out through port 5 and drawn inthrough port 2, while valves 7 and 9 prevent reverse flow through ports3 and 4.

For operation of cylinder 6 of the pump an extension 12 projectstherefrom into cylindrical portion 13 of the housing so that end 14 ofthe extension forms a piston head therein. Portion 13 of the housingcommunicates with the inlet port 15 which is adapted for connection witha source of relatively high-pressure fluid. Projecting from the oppositeside of piston 6 are two piston members 16 and 17 which extend intocylindrical portions 18 and 19 of the housing. Pistons 16 and 17 presentapproximately twice the effective projected piston area that is providedby piston 14. The latter piston portion is constantly under pressurefrom the high pressure source through inlet port 15. When pistons 16 and17 have no pressure operating thereagainst obviously the highpressurefluid from inlet 15 will push piston 14 to the left thereby moving largepiston 6 to the" left in a pumping stroke. If pistons 16 and 17 are thensubjected to the high-pressure fluid, by virtue of the fact that theyhave twice the effective piston area of piston 14 they will overcome theforce it exerts and move piston 6 back to the right in a return pumpingstroke. For controlling the admission and exhaust of high-pressure fluidin the cylinders, cylinder portion 18 is provided with a port 21, whilecylinder portion 19 has a port 23. In order to obtain smooth pumpingaction anda constant flow by piston 6, the action in porting cylinders18 and 19 should be atfected as rapidly as possible at either end of thestrokeof piston 6. It is for this reason that the shuttle of thisinvention may be provided to actuate the valve which controls theporting of cylinders 18 and 19.

The construction and action of the shuttle can be seen in the sectionalview of Fig. 3. Integrally connected to the main piston of the pump isan elongated trigger member 26. This member projects from the piston andinto bore of shuttle member 27 within which it terminates at an enlargedend 28 substantially the dimensions of the interior of the shuttle.Trigger member 26 has a bore 29 therethrough so that high-pressure fluidis distributed thereby to the portions of the interior of the shuttlebeyond trigger lobe 28. Opening 31 extends through the remainder of theshuttle member which projects into portions of the housing defining achamber 33. Passageway 31 thereby conducts pressurized fluid, which hasbeen introduced into the shuttle member by the trigger member, tochamber 33 so that it reacts against end 34 of the shuttle which acts asa piston member.

Reciprocal within counter-cylinder portions 35 and 36 of the housing arecounter-piston members 37 and 38 which are attached to the shuttlemember in any suitable manner such as illustrated at 39 and 40 where theends of the counter-pistons engage projecting shoulder 41 of theshuttle. The limit of the stroke through which the shuttle can operatemay be defined by shoulders 43 and 44 of the housing. Counter-pistons 37and 38 are reciprocal with the shuttle and, for all practical purposes,are

3 integral therewith. Counter-pistons 37 and 38 define approximatelytwice the effective pressure area of end 34 of the shuttle so that whencounter-cylinders and 36 are pressurized the force on pistons 37 and 38will over= come that exerted by piston portion 34 and move the shuttlethrough its stroke to the left. Aperture prevents entrapment of fluid tothe left of the counter-pistons. if cylinders 35 and 36 are ported toexhaust, the force on end 34 of the shuttle will move the shuttlethrough its stroke to the right. By the provisions of this invention theporting of cylinders 35 and 36 will cause the shuttle to move with greatrapidity when the trigger member has teacher either end of its stroke.

In order to provide the fast shuttle action cylinders 35 and 36 eachhave actuating port means at either end thereof. Thus ports-46 'and 47communicate with cylinder 35 while ports 43 and 49 connect with cylinder36. These ports are adapted to communicate with. oppositely disposedactuating port means and 51 of the shuttle. As shown in Fig. 3 the mainpiston 6 of the purnp is midway through its stroke to the right so thatend lobe 28 of the shuttle is disposed between port means 59 and 51 ofthe shuttle member. This means that ports 50 to the left of the lobe aresubjected to high pressure from the highpressure inlet through the boreof the trigger member, while ports 51 communicate, through bore 25, withthe interior of the pump case which is at low pressure and thus acts asan exhaust. In this position ports 47 and 49 communicate with ports 51so that the interiors of counter-cylinders 35 and 36 are ported toexhaust. This enables the high-pressure fluid against end 34 of theshuttle member to force the shuttle member to the right end of itsstroke, as'shown.

The operational cycle of the shuttle member can be understood byreference to Figs. 3, 4 and 5. Trigger member 26 will continue to theright from the position of Fig. 3 with the main pump piston untiltrigger lobe 28 has just passed ports 51 of the shuttle. At that instantports 51 are no longer open to exhaust, but are subjected to pressur zedfiuid from the trigger member. Highpressure fluid then flows through theinterior bore of the trigger member, and through port means 51 and ports47 and 49 to the interior of counter-cylinders 35 and 36. Note that inthis position ports 50 are closed so that no fluid passes into thecounter-cylinders from these ports. When the counter-cylinders aresubjected to the high-pressure fluid from ports 47 and 49 the force onthe counter pistons overcomes the force exerted on end 34 of the shuttlemem her and begins to move the shuttle to the left. As the shuttlecontinues in this movement port means 51 will reach a position as shownin the fragmentary view of Fig. 4 where they no longer communicate withports 47 and 49, but have passed beyond these ports. However, thespacing of the counter-cylinder ports is so arranged that port means 50will be uncovered prior to the closing of ports 51 so that pressurizedfiuid can always enter cylinders 35 and 36 as the shuttle moves throughits stroke to the left. The shuttle can thus continue in its strokeuntil it reaches the left end thereof as illustrated in Fig. 5. In thisend position p'o'rt m'ea'ns 50 remain in communication with ports 46 and48 while ports 51 no longer open to ports 47 and 49. By virtue of thefact that counter-cylinders 35 and 36 are continually subjected tohigh-pressure fluid throughout the length and at the end of thestroke'of counter pistons 37 and 38, the action of the shuttle in movingto the left will be extremely rapid, taking place almost instantaneouslywhen compared with a relatively slow movement of main piston 6 of thepump. It should be observed that the movement of the shuttle is to theleft, opposite from'the direction oftravel of the trigger member. Theinitial shuttle movement causes further opening of ports 4''; and s9so-that-t he shuttle ean rapidl pick u s eed ash pro-'- eeeas throughits stroke; This may be contrasted with a followup type of valve whichtends to follow th'e'ttrove- 4 ment of its actuating member and to closethe port openmgs.

When the main pump piston then starts back through its stroke to theleft, no movement of the shuttle will occur when trigger lobe 28 passesports 51 thereof because these ports, as above stated, have been closedoff. However, the instant the trigger member reaches the left end of itsstroke, (shown in phantom in Fig. 5) and lobe 28 passes ports 50, therewill be an open passageway through ports 46 and 48, and ports 50, to thelow-pressure interior of the pump, thus providing an exhaust forcounter-cylinders 3S and 36. The high-pressure fluid on end 34 of theshuttle then meets no opposition from the counter-pistons and moves theshuttle back to the right. During this movement ports 50 will pass ports46 and 48 so that they are no longer in communication therewith.However, by proper spacing of the ports of the shuttle and the housing,ports 51 will have opened to ports 47 and 49 before ports 50 are closed.This is in the same manner that ports 50 opened prior to the closing ofports 51 where the shuttle moved to the left. This port arrangementmeans that the counter-cylinders are always open to exhaust throughoutthe movement of the shuttle in its stroke to the right, and at the endof the stroke. Again the direction of movement is opposite from that ofthe trigger member, and initial movement of the shuttle causes furtheropening of the ports. By virtue of this fact, the movement to the rightis very rapid and practically instantaneous compared with the slowermovement of the main piston. The pump piston then again travels to theright so that trigger lobe 28 first passes ports 50, which are closedand thus ineffective, and eventually passes ports 51, and the cycle isrepeated.

in the embodiment illustrated the purpose of the rapid movement of theshuttle member, as previously stated, is to effect a valving action forcylinders 18 and 19 of the pump. Therefore, shuttle member 27 serves asa fluid distributing member for the main pump counter cylinders. Asshown in Fig. 6 the interior passageway 25 through the shuttle membercommunicates with an additional fluid distributing port means 55. Whenthe shuttle member is at the right end of its stroke, port means 55communicate with ports 21 and 23 which connect with cylinders 18 and 19respectively. This means that high-pressure fluid from the high-pressureinlet passes through the trigger member, the shuttle member, and throughthese ports into cylinders 18 and 19 for forcing pistons 16 and 17 tothe right. This force of the high pressure-fluid, as described above,moves piston 6 through its stroke to the right. When the piston hasreached the right-hand end of its stroke, and the trigger member is thusmoved through its stroke to the right, the shuttle member is caused torapidly move to the left. When this occurs ports 21 and 23 of cylinders18 and 19 are then connected through annular port '60 with outletpassage 61, as shown in the fragmentary view of Fig. 7. Aperture 62provides an exhaust from the housing for this fluid. Counter-cylinders18 and 19 are thus rapidly ported to exhaust so that the high-pressurefluid against piston 14 can move main piston 6 back through its stroketo the left. The shuttle member thus provides a very rapid portingaction for the counter-cylinders of the pump so that there ispractically no hesitation when piston 6 reaches either end of itsstroke, whereby pumping action thereof is steady and continuous.

It can be readily appreciated from the above description that it is notnecessary for the shuttle member toincorporate a valve as shown anddescribed above. The trigger member could be connected with any sourceof pressurized fluid and moved back and forth by any suitable means. Theshuttle member 27 could be arranged to actuate, for example, an electricswitch: at either and. of its stroke so that slower movement of-thetr-i'gger membeicould. "cause rapid movement of the switch wheat-actrigger member was at eitherend of its stroke. Avar'iety of mechanicalor electrical devices could be attached to the shuttle member so thatthe shuttle could cause rapid movement thereof. In such case of coursethere would be no pump piston and no cylinders 18 and 19, and theshuttle member would not be provided with port 55.

The above detailed description, therefore, illustrates an improved,rapidly acting shuttle member whereby when a trigger member passesthrough its stroke in either direction, extremely rapid action of theshuttle member will take place at the ends of the stroke of this triggermember. By virtue of the fact that the ports to the shuttle member arenot closed throughout and at the ends of its stroke the shuttle willcontinue through its stroke with undiminished velocity until it reachesthe extremity thereof, thus providing the fast action of the shuttle.

The foregoing detailed description is to be clearly understood as givenby way of illustration and example only, the spirit and scope of thisinvention being limited only by the appended claims.

I claim:

1. A shuttle device comprising a body; a shuttle member reciprocaltherein; oppositely disposed fluid responsive means integral with saidshuttle and operable in response to fluid pressure to effect saidreciprocal movement thereof; a trigger member having means forintroducing pressurized fluid into said body, said trigger member beingreciprocal relative thereto, said shuttle and said body having portmeans therein for receiving fluid from said trigger member anddistributing said fluid to said oppositely disposed fluid responsivemeans for operation thereof, said port means being spaced wherebyoperation of said fluid responsive means is obtained at opposite ends ofthe stroke of said trigger member and said fluid responsive means arefully operable throughout the stroke of said trigger member in eitherdirection and at the termination thereof.

2. A device as recited in claim 1 in which said body has first andsecond cylindrical portions therein, and said first fluid responsivemeans comprises an end portion of said shuttle member closely fitted insaid first cylindrical portion of said body member to thereby define apiston, and in which said second fluid responsive means comprises twocounter-piston means integrally attached to said shuttle member andclosely fitted in said second cylindrical portion of said body member.

3. A shuttle device comprising a body; a shuttle member reciprocalthrough a stroke therein, said shuttle having oppositely disposed fluidresponsive means for eifecting said reciprocal movement thereof, saidshuttle member having a port whereby one of said fluid responsive meansis adapted for continual connection with a source of pressurized fluid,the second fluid responsive means being adapted for intermittentconnection with a source of pressurized fluid, said second fluidresponsive means being of greater efliective area than said first meanswhereby when said second means is subjected to pressurized fluid theforce exerted thereby overcomes the force on said first fluid responsivemeans and moves said shuttle member in one direction through its stroke,and when said second fluid responsive means is ported to exhaust saidforce of said first fluid responsive means moves said shuttle memberthrough its stroke in the opposite direction; port means in said shuttlefor admitting fluid to said first fluid responsive means; actuating portmeans in said body and in said shuttle for admitting fluid to andexhausting fluid from said second fluid responsive means; and a triggermember reciprocal in said shuttle and cooperating with said port means,said member being adapted for connection with a source of pressurizedfluid and having fluid passage means therein whereby pressurized fluidis continually admitted to said first fluid responsive means, andintermittently connected with said port means in said body and saidshuttle when said trigger member is at opposite ends of its stroke foreflecting said reciprocal movement of said shuttle, said actuating portmeans being arranged to provide constant connection with said source ofpressurized fluid and with said exhaust during said opposite movementsof said shuttle and at the termination thereof.

4. A device as recited in claim 3 in which said body member is providedwith a cylindrical portion dimen sioned to receive an end of saidshuttle member whereby said end forms said first fluid responsive means,and said body member is provided with two additional cylindricalportions each dimensioned to receive portions of said shuttle memberwhereby said portions form pistons comprising said second fluidresponsive means, said actuating port means being axially displaced andcommunicating with said additional cylindrical portion.

5. A shuttle device comprising a body member, said body member having anexhaust means; a shuttle member reciprocal through a stroke therein,said shuttle member having a first piston portion responsive topressurized fluid for moving said shuttle in one direction, and a secondpiston portion of greater area responsive to pressurized fluid formoving said shuttle in the opposite direction, said shuttle having ahollow interior and a first port means communicating therewith wherebysaid first piston portion continuously communicates with said hollowinterior; and a trigger member reciprocal within said hollow interior ofsaid shuttle, said trigger member having a bore therethrough adapted forconnection with a source of pressurized fluid, and a lobe engaging saidshuttle interior for distributing pressurized fluid on one side of saidlobe while the opposite side thereof communicates with said exhaust,whereby said trigger member cooperates with said first port means toprovide constant fluid pressure to said first piston means, said shuttleand said body having actuating port means for cooperation with saidtrigger lobe whereby said second piston portion communicates with saidexhaust means during the entire movement of said shuttle through itsstroke in said one direction, and communicates with said interior toreceive pressurized fluid during the entire movement of said shuttlethrough its stroke in said opposite direction.

6. A device as recited in claim 5 in which said shuttle member interiorincludes a hollow cylindrical portion open on one end to said exhaustmeans, and said trigger member reciprocates therein, said lobe beingdimensioned for close association therewith whereby the interior of saidshuttle member is subjected to pressurized fluid on one side of saidlobe, said shuttle member actuating port means being aperturestherethrough disposed at axially spaced locations spaced a greateramount than said shuttle member apertures for cooperation therewith,whereby said communication is maintained through said movement of saidshuttle.

7. A shuttle device comprising a body, said body having a firstcylindrical means provided with actuating port means at either endthereof, and a second cylindrical means in communication with saidactuating port means; an elongated cylindrical shuttle member reciprocalthrough a stroke in said first cylindrical means, said shuttle memberhaving port means at either end thereof for cooperation with said bodyport means; piston means in said second cylindrical portion, said pistonmeans including projecting portions engaging said shuttle member forreciprocal movement therewith; a trigger member reciprocal in saidshuttle member, said trigger member having a central passageway adaptedto transmit pressurized fluid to the interior of said shuttle member andhaving a lobe closely fitted within said interior, said shuttle memberand said body having exhaust means on one side of said trigger lobe,said shuttle member includ ing a piston portion having port means inconstant com munication with said interior, said piston portion having asmaller eifective area than that of said piston means, whereby when saidtrigger member is at one end of its stroke pressurized fluid admittedbysaid trigger'membe'r' passes through said actuating port means to saidsecond cylindrical portion for reacting thereagainst whereby said pistonmeans and said shuttle member are moved through a stroke in onedirection, said actuating port means being spaced whereby said actuatingport means remain open throughoutsaid stroke and at the terminationthereof, and when said trigger member is at the other end of its strokesaid port means communicate with said exhaust means whereby said secondcylindrical portion is exhausted of said fluid, and pressure againstsaid piston portion moves said shuttle through a return stroke in theopposite direction, said port means remaining open to said exhaustthroughout said return stroke and at the termination thereof. 7

8. A device as recited in claim 7 in which said actuating port means forsaid shuttle member comprise axially spaced radially disposed aperturemeans, and said actuating port means for said body member compriseaperture means axially spaced a greater distance than said shuttlemember actuating port means, whereby said continual port openings aremaintained during said movement of said shuttle member.

9. A shuttle device comprising a body member having an exhaust, saidbody member having actuating port means therein; a shuttle memberreciprocal within said body, said shuttle member having actuating portmeans for cooperation with said body member actuating port means, andhaving port means communicating with said exhaust, said shuttle memberhaving a first pressure area on one side thereof and a second and largerpressure area on the opposite side thereof, a trigger member in saidbody member in engagement with said shuttle member, said trigger memberprojecting beyond said body for'external operation thereof between twoextreme positions, said trigger member being adapted for connection witha source of pressurized fluid whereby said fluid is continuouslytransmitted to said first pressure area, and said actuating port meansinterconnect said second pressure area with said pressurized fluid whensaid trigger member is in one extreme position, and interconnect saidsecond pressure area with said exhaust when said trigger member is inthe other extreme position whereby when said second pressure area isconnected with said exhaust, said pressurized fluid on said firstpressure area urges said shuttle through a stroke in one direction, andwhen said second pressure area is subjected to pressurized fluid saidfluid urges said shuttle through a stroke in the opposite direction,said actuating port means being spaced whereby said connection to saidexhaust is maintained throughout said stroke in said first direction andsaid connection to said pressurized fluid is maintained throughout saidstroke in said opposite direction.

10. A device as recited in claim 9 in which said port means are spacedwhereby said fluid is transmitted through port means at one end of saidshuttle and said body member during the first part of the stroke of saidshuttle, whereupon such movement closes said port means and opens theport means at the opposite end of said shuttle and body member, saidopening taking place prior to said closing of said firstly mentionedport means, said lastly mentioned port means remaining open throughoutsaid stroke and at the termination thereof.

11. A shuttle device comprising a body; a shuttle reciprocal in saidbody, said shuttle having a bore therethrough, one portion of saidshuttle forming a piston communicating with said bore and responsive tofluid pressure for moving said shuttle, in one direction; a triggermember reciprocal through a stroke in said bore, said trigger memberhaving aperture means therethrough and a lobe complementary to saidbore, said trigger member being adapted for connection with a source ofpressurized fluid whereby said fluidpasses through said membe to saidshuttle member and engages said piston portion thereof, port, means insaid body; port means in said shuttle, communicable therewith, said portmeans in saidbody communicating with counter-cylinder means. therein;

piston means reciprocal in said counter-cylinder means and connectedwith said' shuttle, asid counter-cylinder piston means having greaterarea than that of said shuttle piston portion whereby when pressurizedfluid is admitted into said counter-cylinder means said counter-cylinderpiston means overcome the forceof said fluid on said shuttle pistonportion and move said shuttle in one direction, and when saidcounter-cylinder means are ported to exhaust said fluid against saidpiston portion moves said shuttle member in the opposite direction, saidtrigger member being operable at opposite ends of its stroke to conductpressurized fluid to said port means, and to connect said port meanswith said exhaust, said port means being spaced to remain open theentire length and at the end of the stroke of said shuttle in eitherdirection.

12. A shuttle device comprising a body member, said body member havingan exhaust means; a shuttle member reciprocal through a stroke in saidbody member; a trigger member reciprocal through a stroke in said bodymember, said trigger member having a lobe associated with said shuttlemember and having a portion projecting from said body for externalactuation thereof, said trigger member having passage means therethroughadapted for connection with a source of pressurized fluid wherebypressurized fluid is transmitted to one side of said lobe, and the otherside thereof communicates with said exhaust means; said shuttle memberhaving a pressure area on one side thereof and port means communicatingtherewith whereby said pressure area is constantly subjected to fluidpressure from said trigger member, said shuttle memher having. a secondpressure area on the other side thereof; said body member and saidshuttle member having port means communicating with said second pressurearea whereby when said trigger member is at one end of its stroke saidsecond pressure area receives pressurized fluid from said port means formoving the said shuttle member through its stroke in one direction, andwhen said trigger member is at the other end of its stroke said secondpressure area communicates through port means with said exhaust wherebysaid pressure on said first pressure area moves said shuttle memberthrough its stroke in the opposite direction, said actuating port meansbeing arranged whereby constant communication with said pressurizedfluid is maintained therethrough during the entire movement of saidshuttle member through its stroke in said one direction, and constantcommunication with said exhaust means is maintained through said portmeans the entire length of the stroke of said shuttle in said oppositedirection.

13. A shuttle device comprising a body member having an exhaust, and afirst and a second cylindrical portion; a shuttle member reciprocalwithin a complementary portion of said body member, said shuttle memberhaving a hollow interior communicating with saidexhaust; a triggermember in said shuttle member and reciprocal through a stroke relativethereto, said trigger member having an enlarged lobe closely fittedwithin said interior of said shuttle member, said trigger memberprojecting from said body member for external actuation thereof andbeing provided with a fluid passage means therethrough whereby saidmemberis adapted to be connected with a source of pressurized fluid fortransmitting said fluid to the interior of said shuttle beyond said lobewhereby said interior beyond said lobe is subjected to said pressurizedfluid, and said interior on the opposite side of said lobe is connectedwith said exhaust, said shuttle member having an end thereof closelyfittedwith' said first cylindrical portion of said body member, andprovided with fluid passage means interconnecting said hollow interiorand saidcndportion whereby said end-por tion comprises a first pistonconstantly subjected to said pressurized fluid, said shuttle memberhaving attached thereto a second piston portion of greater area thansaid first piston closely fitted within said second cylindrical portionof said body member, said shuttle member having axially displacedactuating port means communicating with said hollow interior, and saidbody member having axially displaced actuating port means forcooperation therewith and communicating with said second cylindricalportion whereby when said trigger member is at one end of its strokesaid hollow interior is in communication with said exhaust and saidactuating port means interconnect said second cylindrical portion withsaid exhaust whereby said fluid pressure against said first piston movessaid shuttle through its stroke in one direction, and when said triggermember is at the opposite end of its stroke said hollow interior portionis subjected to said pressurized fluid whereby said actuating port meansconnect said interior and said second cylindrical portion for subjectingsaid second piston portion to said pressurized fluid and moving saidshuttle through its stroke in the opposite direction, said actuatingport means in said body member being spaced apart a greater amount thatsaid actuating port means in said shuttle member and disposed wherebyconstant communication with said exhaust is maintained throughout saidmovement of said shuttle in said one direction and at the terminationthereof, and constant communication with said pressurized fluid ismaintained throughout said stroke of said shuttle member in saidopposite direction and at the termination thereof.

References Cited in the file of this patent UNITED STATES PATENTS245,777 Brazelle Aug. 16, 1881 539,339 Breitenstein May 14, 18951,125,980 Dodds Jan. 26, 1915 1,938,021 Hobson Dec. 5, 1933

